Positive lithium supplement agent, preparation method thereof, positive plate, battery and electric equipment

Abstract

According to the positive electrode lithium supplement agent and the preparation method thereof, the positive plate, the battery and the electric equipment provided by the embodiment of the invention, the lithium content of the first lithium supplement agent is higher than the lithium content of the second lithium supplement agent, and the lithium removal voltage corresponding to the first lithium supplement agent is higher than the lithium removal voltage corresponding to the second lithium supplement agent; the current is preferentially distributed to the second lithium supplement agent with lower lithium removal voltage in the lithium removal process, so that the electrochemical reaction rate of the first lithium supplement agent can be controlled, the generation of oxygen free radicals in the lithium removal process of the first lithium supplement agent is inhibited, and the gas production rate of the first lithium supplement agent is reduced. One of the first lithium supplement agent and the second lithium supplement agent coats at least part of the surface of the other one, so that the distance between particles of the first lithium supplement agent and the second lithium supplement agent can be shortened, and the second lithium supplement agent can effectively perform charge compensation on the first lithium supplement agent; therefore, the increase of the valence state of the metal can be inhibited in the lithium removal process of the first lithium supplement agent, the occurrence of side reactions is reduced, and the capacity retention rate of the battery can be effectively improved.

Description

Technical Field

[0001] This application relates to the field of batteries, and in particular, to a positive electrode lithium supplement, a preparation method thereof, a positive electrode sheet, a battery, and an electrical device. Background Art

[0002] In a lithium-ion battery, the loss of lithium is an important factor affecting the battery capacity.

[0003] Currently, mainly through lithium supplementation technology, an additional lithium source is added during the battery manufacturing process to compensate for the irreversible lithium loss in the first charge-discharge cycle, which helps to improve the initial capacity of the battery.

[0004] However, when the additional lithium source de-lithiates, there may be problems such as a large amount of gas generation and many side reactions, which affect the capacity retention rate of the battery. Summary of the Invention

[0005] Embodiments of this application provide a positive electrode lithium supplement, a preparation method thereof, a positive electrode sheet, a battery, and an electrical device to reduce gas generation and improve battery performance.

[0006] In a first aspect, embodiments of this application provide a positive electrode lithium supplement, including:

[0007] A first lithium supplement and a second lithium supplement, wherein one of the first lithium supplement and the second lithium supplement is coated on at least part of the surface of the other;

[0008] The lithium content of the first lithium supplement is higher than that of the second lithium supplement;

[0009] The chemical formula of the first lithium supplement includes Li a M b O c , where M is at least one of Ni, Cr, Co, Mn, Fe, Al, Cu, V, Ti, Re;

[0010] 0 < a ≤ 6, 0 < b ≤ 3, 0 < c ≤ 6;

[0011] And / or, the chemical formula of the second lithium supplement includes Li x N y O z , where N is at least one of Ni, Cr, Co, Mn, Fe, Al, Cu, V, Ti, Ru, Mo;

[0012] 0 < x ≤ 3, 0 < y ≤ 3, 0 < z ≤ 4.

[0013] In a possible implementation manner, the first lithium supplement includes Li 5 FeO 4 , Li 6 CoO 4, Li 4 CoO 4 , Li 5 ReO 6 at least one of;

[0014] and / or, the second lithium supplement includes Li 2 NiO 2 , Li 2 RuO 3 , Li 2 MnO 3 , Li 2 MoO 3 , Li 0.65 Ni 1.35 O 2 at least one of.

[0015] In a possible implementation, at least part of the surface of the positive electrode lithium supplement is coated with a carbon coating layer.

[0016] In a possible implementation, the mass ratio of the carbon coating layer to the positive electrode lithium supplement is 0.1% - 5%.

[0017] In a possible implementation,

[0018] before the first lithium supplement de-lithiation, the valence state of M exists in at least one of +2, +3, +4, and +7;

[0019] and / or, after the first lithium supplement de-lithiation, the valence state of M exists in at least one of +3 and +4.

[0020] In a possible implementation, the volume of the first lithium supplement after de-lithiation is 40% - 80% of the volume of the first lithium supplement before de-lithiation;

[0021] and / or, the volume of the second lithium supplement after de-lithiation is 70% - 90% of the volume of the second lithium supplement before de-lithiation.

[0022] In a possible implementation, the de-lithiation voltage of the first lithium supplement is 3.4V - 4.4V;

[0023] and / or, the de-lithiation voltage of the second lithium supplement is 3.4V - 4.5V.

[0024] In a possible implementation, the mass ratio of the second lithium supplement to the first lithium supplement is 10:100 - 70:100.

[0025] In a possible implementation, the Dv50 of the first lithium supplement is 1μm - 15μm;

[0026] And / or, the Dv50 of the second lithium supplement is 0.2 μm to 12 μm.

[0027] In a possible implementation, the charge specific capacity of the first lithium supplement is 400 mAh / g to 1200 mAh / g;

[0028] And / or, the charge specific capacity of the second lithium supplement is 240 mAh / g to 550 mAh / g.

[0029] In a possible implementation, the specific surface area of the positive electrode lithium supplement is 1 m 2 / g - 20 m 2 / g.

[0030] Second, the embodiments of the present application provide a preparation method of the positive electrode lithium supplement described in the first aspect, and the method includes:

[0031] Mix the first lithium supplement and the second lithium supplement and then perform sintering treatment to obtain the positive electrode lithium supplement.

[0032] In a possible implementation, mixing the first lithium supplement and the second lithium supplement and then performing sintering treatment includes:

[0033] Perform a first sintering treatment on the first lithium supplement precursor to obtain the first lithium supplement;

[0034] Perform a second sintering treatment on the second lithium supplement precursor to obtain the second lithium supplement;

[0035] Mix the first lithium supplement, the second lithium supplement and a carbon source and perform a third sintering treatment.

[0036] In a possible implementation, the temperature of the first sintering treatment is lower than the temperature of the third sintering treatment;

[0037] And / or, the temperature of the second sintering treatment is lower than the temperature of the third sintering treatment.

[0038] In a possible implementation, the temperature of the first sintering treatment is 350 °C - 650 °C;

[0039] And / or, the temperature of the second sintering treatment is 350 °C - 650 °C;

[0040] And / or, the temperature of the third sintering treatment is 650 °C - 900 °C;

[0041] And / or, the time of the first sintering treatment is 2 h - 24 h;

[0042] And / or, the time of the second sintering treatment is 2 h - 24 h;

[0043] And / or, the time of the third sintering treatment is 2h - 24h.

[0044] In a third aspect, an embodiment of the present application provides a positive electrode sheet, which includes the positive electrode lithium supplement agent described in the first aspect or the positive electrode lithium supplement agent prepared by the preparation method of the positive electrode lithium supplement agent described in the second aspect.

[0045] In a fourth aspect, an embodiment of the present application provides a battery, which includes the positive electrode sheet described in the third aspect.

[0046] In a fifth aspect, an embodiment of the present application provides an electrical device, which includes the battery described in the fourth aspect.

[0047] The positive electrode lithium supplement agent, its preparation method, positive electrode sheet, battery and electrical device provided by the embodiments of the present application include a first lithium supplement agent and a second lithium supplement agent. The lithium content of the first lithium supplement agent is higher than that of the second lithium supplement agent, so the de-lithiation voltage corresponding to the first lithium supplement agent is higher than the de-lithiation voltage corresponding to the second lithium supplement agent. During the de-lithiation process, the current is preferentially distributed to the second lithium supplement agent with a lower de-lithiation voltage, thereby controlling the electrochemical reaction rate of the first lithium supplement agent, inhibiting the generation of oxygen free radicals during the de-lithiation process of the first de-lithiation agent, and reducing the gas generation amount of the first lithium supplement agent. And one of the first lithium supplement agent and the second lithium supplement agent is coated on at least part of the surface of the other, which can shorten the distance between the particles of the first lithium supplement agent and the second lithium supplement agent, enabling the second lithium supplement agent to effectively compensate the charge of the first lithium supplement agent, thereby inhibiting the increase of the metal valence state during the de-lithiation process of the first lithium supplement agent and reducing the occurrence of side reactions. By reducing the gas generation amount of the first lithium supplement agent and the occurrence of side reactions, the capacity retention rate of the battery can be effectively improved. Description of the Drawings

[0048] The drawings here are incorporated into the description and form a part of this description, showing embodiments consistent with the present application, and are used together with the description to explain the principles of the present application.

[0049] Figure 1 It is a schematic structural diagram of a positive electrode lithium supplement agent provided by the present application;

[0050] Figure 2 It is a schematic structural diagram of another positive electrode lithium supplement agent provided by the present application.

[0051] Through the above drawings, the clear embodiments of the present application have been shown, and there will be more detailed descriptions later. These drawings and text descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. Detailed Embodiments

[0052] Exemplary embodiments will be described in detail herein, and examples thereof are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0053] With the progress of technology and the growth of market demand, higher requirements are put forward for power batteries and energy storage batteries, especially in terms of energy density, cycle life, and calendar life. In lithium-ion batteries, the loss of lithium is an important factor affecting battery capacity. The lithium supplementation technology compensates for the irreversible lithium loss in the first charge-discharge cycle by adding an additional lithium source during battery manufacturing, which helps to increase the initial capacity of the battery, thereby improving the energy density, cycle life, and calendar life.

[0054] For example, the material system of ternary lithium batteries is developing towards high-nickel cathodes and silicon-based anodes. Among them, the silicon-based anode can include silicon monoxide and graphite. During the first charging process of lithium-ion batteries, lithium ions are removed from the cathode material and embedded into the silicon monoxide anode material, thereby consuming part of the lithium. This process can also be called the effective lithium consumption during the first lithium intercalation of silicon monoxide. The lithium supplementation technology can supplement the effective lithium consumed by the first lithium intercalation of silicon monoxide in ternary lithium batteries, thereby improving the energy density of the battery and simultaneously improving the cycle life and calendar life of the battery.

[0055] Another example is that while optimizing the material system to improve the energy density of lithium iron phosphate batteries, they are also continuously developing in the directions of improving the cycle life and storage performance of the battery. For example, when the material system is a lithium iron phosphate cathode and a graphite anode, the lithium supplementation technology can improve the energy density of the battery to a certain extent, and at the same time, pre-stored lithium can be introduced into the battery system. The pre-stored lithium continuously supplements the active lithium consumed during battery cycling, thus significantly improving the cycle life and storage performance of the battery. In addition, in order to further improve the energy density of the battery, an anode with a high specific capacity can be selected, such as an anode composed of a composite of silicon-based and graphite. The selectable material system is a lithium iron phosphate cathode and an anode of silicon monoxide plus graphite. However, due to the low initial Coulomb efficiency of the anode, lithium in the cathode material is irreversibly consumed, which limits the improvement of the battery energy density. The lithium supplementation technology can introduce exogenous lithium to make up for the irreversibly consumed effective lithium. In addition, the applicant considers that although the capacity of lithium iron phosphate manganese is not much different from that of lithium iron phosphate, it has a higher working voltage. It can be considered to combine a lithium iron phosphate manganese cathode with a silicon-based plus graphite anode and combine the lithium supplementation technology to further improve the energy density, cycle life, and calendar life of the battery.

[0056] Currently, the lithium supplementation techniques that can be achieved include: lithium supplementation at the negative electrode, lithium supplementation at the positive electrode, lithium supplementation in the electrolyte, lithium supplementation on the separator, lithium supplementation on the current collector, and electrochemical lithium supplementation. Among them, lithium supplementation at the positive electrode can directly add the positive electrode lithium supplement agent to the positive electrode slurry during the homogenization process, with relatively low requirements for improving the lithium supplementation process, without the need to transform the production environment and equipment, and is more suitable for the existing lithium-ion battery manufacturing process.

[0057] The existing positive electrode lithium supplement agents can be divided into three categories: The first category is binary lithium-containing compounds, such as Li 2 O, Li 2 O 2 、LiF、Li 2 S、Li 3 N, etc.; The second category is ternary lithium-containing compounds, such as Li 5 FeO 4 、Li 6 CoO 4 、Li 4 CoO 4 、Li 2 NiO 2 、Li 5 ReO 6 、Li 2 RuO 3 、Li 2 MnO 3 、Li 2 MoO 3 、Li 0.65 Ni 1.35 O 2 , etc.; The third category is organic lithium salts, such as Li 2 DHBN (3,4-dihydroxybenzonitrile dilithium salt), Li 2 C 2 O 4 、Li 2 C 4 O 4 、Li 2 C 3 O 5 、Li 2 C 4 O 6 , etc.

[0058] However, the decomposition voltages of the positive electrode lithium supplement agents in the first and third categories are high and the gas generation is serious, which affects the effectiveness of such lithium supplement agents in practical applications. Among the positive electrode lithium supplement agents in the second category, Li 5 FeO 4 and Li 2 NiO 2 use low-cost metals and have relatively low decomposition voltages, making the use of these two lithium supplement agents increasing in practical applications.

[0059] However, Li 2 NiO 2 has a lower discharge capacity and a higher reversible capacity, resulting in less effective lithium in Li 2 NiO 2 that can be used as a lithium supplement source. For example, the theoretical discharge capacity is 340 mAh / g, and the actual reversible capacity is 83 mAh / g. The effective lithium in Li 2 NiO 2 that can be used as a lithium supplement source is 76%. While Li 5 FeO 4 has a relatively high theoretical specific capacity (such as 867 mAh / g), and in practical applications, about 4 Li+ are removed during the first de-lithiation, making the irreversible lithium as a lithium source 693 mAh / g. Therefore, considering the lithium supplementation effect, Li 5 FeO 4 is more suitable as a cathode lithium supplement agent.

[0060] The applicant found that Li 5 FeO 4 as a cathode lithium supplement agent is mainly applied by directly adding it to the cathode slurry. The cathode electrode sheet is obtained by the coating-baking method, and uniformly distributed Li 5 FeO 4 particles are contained in the active film layer of the electrode sheet. Currently, the added Li 5 FeO 4 particles have a relatively large particle size (Dv50 is 7 μm - 9 μm), which is one order of magnitude larger than that of the lithium iron phosphate cathode active material, making Li 5 FeO 4 able to release 4 effective Li+ more completely at a relatively high decomposition voltage (such as 4.3 V). During this process, while Li 5 FeO 4 is de-lithiated, Fe undergoes an oxidation reaction, resulting in the valence state of Fe rising from +3 to +4, generating Fe oxide residues. These residues may slowly release oxygen or oxygen free radicals during the charge-discharge process, and a large amount of oxygen is also released during the de-lithiation process, causing serious gas generation during the battery cycle or storage process. In addition, the dissolution of metals (Ni and Fe) will also increase the safety risk.

[0061] Currently, the research on cathode lithium supplement agents mainly focuses on the selection of the lithium supplement agent itself, as well as the synthesis, material composition, and structure optimization of the cathode lithium supplement agent. For example, the performance of the lithium supplement agent is improved by means of coating, doping, or in-situ growth.

[0062] However, there is no optimization for the gas generation and thermal safety of the battery after the lithium supplement agent de-lithiation, resulting in negative impacts such as gas generation and reduced thermal safety during the use of the lithium supplement agent. Moreover, during the de-lithiation process of the lithium supplement agent, the metal may undergo a phase change and the metal valence state may increase, leading to an increase in side reactions in the battery system. The side reactions may include, for example, redox reactions of the metal and decomposition reactions of the catalytic electrolyte. Problems such as gas generation, reduced thermal safety, and increased side reactions during the use of the lithium supplement agent will affect the capacity retention rate of the battery.

[0063] In view of this, an embodiment of the present application provides a cathode lithium supplement agent, which is a secondary particle composed of two different lithium supplement agents, namely a first lithium supplement agent and a second lithium supplement agent, and one of the first lithium supplement agent and the second lithium supplement agent coats at least part of the surface of the other.

[0064] Materials with high lithium content have a higher de-lithiation voltage because lithium ions occupy more lattice sites and stronger Li-O bond binding energy needs to be overcome to extract lithium ions. Therefore, when the lithium content of the first lithium supplement agent is higher than that of the second lithium supplement agent, the de-lithiation voltage corresponding to the first lithium supplement agent is higher than that corresponding to the second lithium supplement agent. During the de-lithiation process, the current is preferentially distributed to the second lithium supplement agent with a lower de-lithiation voltage, thereby controlling the electrochemical reaction rate of the first lithium supplement agent, inhibiting the generation of oxygen free radicals during the de-lithiation process of the first de-lithiation agent, and reducing the gas generation amount of the first lithium supplement agent.

[0065] Moreover, one of the first lithium supplement agent and the second lithium supplement agent coats at least part of the surface of the other, which can shorten the distance between the particles of the first lithium supplement agent and the second lithium supplement agent, enabling the second lithium supplement agent to effectively compensate the charge of the first lithium supplement agent, thereby inhibiting the increase in the metal valence state during the de-lithiation process of the first lithium supplement agent and reducing the occurrence of side reactions.

[0066] By reducing the gas generation amount of the first lithium supplement agent and the occurrence of side reactions, the capacity retention rate of the battery can be effectively improved.

[0067] Exemplarily, the residue after the de-lithiation of the second lithium supplement agent can be a stable oxide, further reducing the gas generation amount of the cathode lithium supplement agent, while helping to stabilize the electrochemical environment around the first lithium supplement agent and the second lithium supplement agent, facilitating the control of the dissolution of the metal in the first lithium supplement agent and the second lithium supplement agent, and further reducing the occurrence of side reactions.

[0068] It should be noted that since the lithium content of the first lithium supplement agent is higher than that of the second lithium supplement agent, the first lithium supplement agent can provide more lithium. Then, the volume ratio of the first lithium supplement agent after de-lithiation to that before de-lithiation is smaller than the volume ratio of the second lithium supplement agent after de-lithiation to that before de-lithiation. The cathode lithium supplement agent proposed in the embodiment of the present application is a secondary particle composed of the first lithium supplement agent and the second lithium supplement agent, that is, the first lithium supplement agent, the second lithium supplement agent, and the cathode lithium supplement agent can exist in the form of particles.

[0069] Exemplarily, lithium deintercalation can cause cracks, pores or lattice distortion in the material. Through FIB-SEM (focused ion beam-scanning electron microscope) high-resolution cross-sectional imaging, the degree of morphological damage in different regions can be compared. The region with more severe damage usually corresponds to a higher amount of lithium deintercalation (lithium content). Using EDS (energy-dispersive X-ray spectroscopy) energy spectrum analysis to analyze the change in the atomic ratio of transition metals (such as Fe, Ni, Co, Mn) to oxygen elements: when the valence state of the transition metal increases (such as → ), it is usually accompanied by the deintercalation of lithium ions, and its non-uniform distribution can indirectly reflect the difference in lithium content.

[0070] In some embodiments, the chemical formula of the first lithium supplementing agent includes Li a M b O c , where M is at least one of Ni, Cr, Co, Mn, Fe, Al, Cu, V, Ti, Re; 0 < a ≤ 6, 0 < b ≤ 3, 0 < c ≤ 6.

[0071] Among them, a represents the number of lithium atoms, which can affect the amount of lithium ions released by the first lithium supplementing agent. b represents the number of metal M, which can affect the electrochemical properties and stability of the first lithium supplementing agent. c represents the number of oxygen atoms, which can affect the crystal structure of the first lithium supplementing agent. 0 < a ≤ 6, 0 < b ≤ 3, 0 < c ≤ 6, so as to meet the lithium supplementing requirements.

[0072] Exemplarily, a can be 0.1, 0.4, 0.7, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6 or the range composed of any two of them.

[0073] b can be 0.1, 0.3, 0.6, 1, 1.4, 1.7, 2, 2.3, 2.6, 2.8, 3 or the range composed of any two of them.

[0074] c can be 0.1, 0.4, 0.7, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6 or the range composed of any two of them.

[0075] In some embodiments, the chemical formula of the second lithium supplementing agent includes Li x N y O z , where N is at least one of Ni, Cr, Co, Mn, Fe, Al, Cu, V, Ti, Ru, Mo; 0 < x ≤ 3, 0 < y ≤ 3, 0 < z ≤ 4.

[0076] Among them, x represents the number of lithium atoms, which can affect the amount of lithium ions released by the second lithium supplementing agent; y represents the number of metal N, which can affect the electrochemical properties and stability of the second lithium supplementing agent; z represents the number of oxygen atoms, which can affect the crystal structure of the second lithium supplementing agent. 0 < x ≤ 3, 0 < y ≤ 3, 0 < z ≤ 4, thereby assisting the first lithium supplementing agent to solve the above problems such as gas generation, phase change, and side reactions.

[0077] Exemplarily, x can be 0.1, 0.3, 0.8, 1.1, 1.2, 1.4, 1.5, 1.7, 1.8, 2, 2.2, 2.4, 2.5, 2.7, 2.9, 3, or a range composed of any two of them.

[0078] y can be 0.1, 0.3, 0.6, 1, 1.4, 1.7, 2, 2.3, 2.6, 2.8, 3, or a range composed of any two of them.

[0079] z can be 0.1, 0.3, 0.6, 1, 1.4, 1.7, 2, 2.3, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, or a range composed of any two of them.

[0080] For example, the first lithium supplementing agent can be lithium-rich lithium ferrite, and the second lithium supplementing agent can be lithium-rich lithium nickelate. During the delithiation process of lithium-rich lithium ferrite, the oxidation of Fe leads to an increase in valence state and becomes an unstable oxidation state, which may cause an increase in side reactions. During the delithiation process of lithium-rich lithium nickelate, the valence state of Ni changes from +2 to +4. The second lithium supplementing agent can act as an electron donor to provide charge compensation for the first lithium supplementing agent during the delithiation process, effectively inhibiting the increase in the metal valence state in the first lithium supplementing agent and reducing the occurrence of side reactions. And one of lithium-rich lithium nickelate and lithium-rich lithium ferrite coats at least part of the surface of the other, which can shorten the distance between the lithium supplementing agent particles, enabling lithium-rich lithium nickelate to more effectively perform charge compensation on lithium-rich lithium ferrite and further reducing the occurrence of side reactions.

[0081] Exemplarily, lithium-rich lithium nickelate can coat at least part of the surface of lithium-rich lithium ferrite, or lithium-rich lithium ferrite can coat at least part of the surface of lithium-rich lithium nickelate. For example, when the particle size of lithium-rich lithium nickelate is smaller than that of lithium-rich lithium ferrite, lithium-rich lithium nickelate coats on the surface of lithium-rich lithium ferrite; when the particle size of lithium-rich lithium ferrite is smaller than that of lithium-rich lithium nickelate, lithium-rich lithium ferrite coats on the surface of lithium-rich lithium nickelate.

[0082] In some alternative embodiments, at least a portion of the surface of the positive electrode lithium supplement agent is coated with a carbon coating layer, which can form a barrier to prevent the invasion of external moisture into the first lithium supplement agent and the second lithium supplement agent, slow down the water absorption failure rate of the first lithium supplement agent and the second lithium supplement agent, and at the same time, the physical barrier formed by the carbon coating layer also effectively reduces the risk of metal dissolution in the residues after lithium deintercalation of the first lithium supplement agent and the second lithium supplement agent.

[0083] In some embodiments, the second lithium supplement agent and the carbon coating layer form a composite coating layer of the first lithium supplement agent, and the water absorption failure of the first lithium supplement agent is improved through the composite coating layer. The carbon coating layer and the second lithium supplement agent form a double coating relative to the first lithium supplement agent, which more effectively prevents the invasion of external moisture into the first lithium supplement agent, and the second lithium supplement agent is tightly connected to the first lithium supplement agent under the restraint of the carbon coating layer and has a rich electron path, so that during the lithium deintercalation process, the current can be preferentially distributed to the second lithium supplement agent, reducing the decomposition polarization of the first lithium supplement agent, and the close physical distance enables the second lithium supplement agent to more effectively provide charge compensation for the first lithium supplement agent.

[0084] Exemplarily, the second lithium supplement agent can coat a part of the surface of the first lithium supplement agent, and the carbon coating layer coats a part of the surface of the first lithium supplement agent and a part of the surface of the second lithium supplement agent, as Figure 1 shown. The second lithium supplement agent can also coat the entire surface of the first lithium supplement agent, and the carbon coating layer coats the entire surface of the second lithium supplement agent.

[0085] In some embodiments, the carbon coating layer is coated on the outer surfaces of the first lithium supplement agent and the second lithium supplement agent, forming a binding effect on the combination of the first lithium supplement agent and the second lithium supplement agent, ensuring the electron path of the first lithium supplement agent and the second lithium supplement agent, improving the lithium ion insertion / extraction path in the two lithium supplement agents, and improving the battery electrochemical performance. And the carbon coating layer can form a barrier to prevent the invasion of external moisture into the first lithium supplement agent and the second lithium supplement agent, slow down the water absorption failure rate of the first lithium supplement agent and the second lithium supplement agent, and at the same time, the physical barrier formed by the carbon coating layer also effectively reduces the risk of metal dissolution in the residues after lithium deintercalation of the first lithium supplement agent and the second lithium supplement agent.

[0086] Exemplarily, the second lithium supplement agent can coat a part of the surface of the first lithium supplement agent, and the carbon coating layer coats the surfaces of the first lithium supplement agent and the second lithium supplement agent, as Figure 2 shown, through the carbon coating layer, the water absorption failure rate of the first lithium supplement agent and the second lithium supplement agent is slowed down, and at the same time, the risk of metal dissolution in the residues after lithium deintercalation of the first lithium supplement agent and the second lithium supplement agent is reduced.

[0087] In some examples, the mass of the carbon coating layer accounts for 0.1% - 5% of the mass of the cathode lithium supplement agent. The mass ratio of the carbon coating layer affects the thickness of the carbon coating layer and also affects the integrity of the carbon coating layer, thereby affecting the power performance, cycle performance, and storage performance of the battery product. Through the above mass ratio, the carbon coating layer can have a more appropriate thickness and integrity, improving the power performance, cycle performance, and storage performance of the battery product.

[0088] For example, the mass ratio of the carbon coating layer in the cathode lithium supplement agent can be 0.1%, 0.5%, 0.8%, 1%, 1.3%, 1.8%, 2%, 2.4%, 2.7%, 3%, 3.5%, 4%, 4.5%, 5% or the range composed of any two of them.

[0089] As an implementation method, the first lithium supplement agent includes Li 5 FeO 4 , Li 6 CoO 4 , Li 4 CoO 4 , Li 5 ReO 6 At least one of them. Then, the lithium content of the first lithium supplement agent is relatively high, so that the energy density of the battery can be increased and the battery cycle life can be extended.

[0090] As an implementation method, the second lithium supplement agent includes Li 2 NiO 2 , Li 2 RuO 3 , Li 2 MnO 3 , Li 2 MoO 3 , Li 0.65 Ni 1.35 O 2 At least one of them. Then, the product after delithiation of the second lithium supplement agent is a stable oxide with a low gas generation amount.

[0091] In some examples, during the first delithiation process of the second lithium supplement agent, as Li+ is removed, the valence state of metal N in the second lithium supplement agent increases, and the valence state form of metal N can be at least one of +2, +3, and +4, so that the residue after delithiation of the second lithium supplement agent is a stable oxide. For example, when the second lithium supplement agent is Li 2 NiO 2 , the residue after delithiation of the second lithium supplement agent is Li 2 NiO 2 , Li 1.5 NiO 2 , LiNiO 2 , Li 0.5NiO 2 、 NiO 2 or at least one of them.

[0092] During the first de-lithiation process of the first lithium supplement agent, as Li+ is removed, the valence state of metal M in the first lithium supplement agent increases. The increase in the valence state of metal M is accompanied by the evolution of oxygen, and there is O 2- 、 O - and other oxygen forms. Correspondingly, the valence state of M exists in at least one of +2, +3, +4, and +7. At this time, M is prone to redox reactions, leading to an increase in side reactions.

[0093] Since the de-lithiation of the second lithium supplement agent can also perform charge compensation on the first lithium supplement agent, reducing the increase in the metal valence state in the first lithium supplement agent, the increase in the metal valence state in the first lithium supplement agent is effectively inhibited, thereby reducing the generation of side reactions. Correspondingly, after the first lithium supplement agent is de-lithiated, the valence state of M exists in at least one of +3 and +4. For example, the first lithium supplement agent is Li 5 FeO 4 , and the product after the first lithium supplement agent is de-lithiated is Li 3 FeO 3.5 、 LiFeO 2 or at least one of them.

[0094] As an implementation method, the valence state of metal M in the first lithium supplement agent, the residue after the first lithium supplement agent is de-lithiated, the valence state of metal N in the second lithium supplement agent, and the residue after the second lithium supplement agent is de-lithiated can be detected by XRD (X-Ray Diffractometer), XPS (X-ray photoelectron spectroscopy), and synchrotron radiation small-angle X-ray. In addition, through the above several detection methods, it can be detected that almost no oxygen and oxygen free radicals are released during the de-lithiation of the second lithium supplement agent.

[0095] In some embodiments, the first lithium supplement agent exists in the form of particles. After the first lithium supplement agent is de-lithiated, the particles of the first lithium supplement agent collapse. The volume of the first lithium supplement agent after de-lithiation is 40%-80% of the volume before de-lithiation. Since the second lithium supplement agent is coated on at least part of the surface of the first lithium supplement agent, particle shrinkage and collapse are reduced, thereby reducing the volume change of the first lithium supplement agent before and after de-lithiation and improving the electrical contact between the cathode active materials.

[0096] In some embodiments, the second lithium supplement agent has low gas generation, and the product after de-lithiation is a stable oxide. Therefore, the volume change of the second lithium supplement agent after de-lithiation is small. The volume of the second lithium supplement agent after de-lithiation is 70%-90% of the volume before de-lithiation.

[0097] As an implementation method, quantification can be carried out through SEM-FIB modeling. The volume of the cavity structure where the lithium supplement agent particles are located after delithiation can be quantified, and the volume of the particles themselves after delithiation can also be quantified.

[0098] It should be noted that the relative positions of the first lithium supplement agent after delithiation and the second lithium supplement agent after delithiation do not change. For example, the second lithium supplement agent after delithiation can be distributed on part or all of the surface of the first lithium supplement agent after delithiation.

[0099] In some embodiments, the delithiation voltage range of the first lithium supplement agent can be 3.4V - 4.4V. Reducing the upper limit of the delithiation voltage can effectively alleviate side reactions inside the battery and reduce the risk of metal dissolution in the residues after the decomposition of the lithium supplement agent. However, too low an upper limit of the delithiation voltage will affect the delithiation depth of the lithium supplement agent and the lithium supplementation effect. Within this voltage range, the decomposition polarization of the first lithium supplement agent is small, so a more gentle phase change occurs during the delithiation decomposition process. And the gentle phase change can make the cracks of the first lithium supplement agent after delithiation smaller and prevent violent volume changes, which helps to provide a stable lithium source and can also provide the thermal stability of the battery and improve the safety of the battery.

[0100] The delithiation voltage range of the second lithium supplement agent can be 3.4V - 4.5V. Within this voltage range, there is no obvious phase change phenomenon during the delithiation process of the second lithium supplement agent, which improves the thermal stability of the battery.

[0101] It should be noted that during the delithiation decomposition process, when the decomposition voltage is higher than 3.65V, the second lithium supplement agent can obtain the decomposition current prior to the first lithium supplement agent, making the decomposition polarization of the first lithium supplement agent smaller, so a more gentle phase change occurs during the delithiation decomposition process.

[0102] For example, the delithiation voltage of the first lithium supplement agent can be 3.4 - 4.3V, further can be 3.4 - 4.1V, and even further can be 3.4 - 4.0V to reduce the decomposition polarization of the first lithium supplement agent.

[0103] The delithiation voltage of the second lithium supplement agent can be 3.4 - 4.3V, further can be 3.4 - 4.1V, and even further can be 3.4 - 4.0V.

[0104] It should be noted that the delithiation voltage of the lithium supplement agent is related to the material of the lithium supplement agent itself.

[0105] As a specific implementation method, the pore distribution of the lithium supplement agent particles can be quantified through SEM-FIB to observe the crack situation of the lithium supplement agent after delithiation, so as to evaluate the rationality of the delithiation voltage.

[0106] In some embodiments, the mass ratio of the second lithium supplement agent to the first lithium supplement agent can be 10:100 - 70:100. The mass ratio of the second lithium supplement agent to the first lithium supplement agent is related to the specific capacity of the cathode lithium supplement agent. The higher the proportion of the second lithium supplement agent, the lower the delithiation specific capacity of the cathode lithium supplement agent, but it can better inhibit the delithiation phase change of the first lithium supplement agent and the increase of the metal valence state in the first lithium supplement agent; the lower the proportion of the second lithium supplement agent, the higher the delithiation specific capacity of the cathode lithium supplement agent. By using the mass ratio within the above range, the lithium secondary battery using the above cathode lithium supplement agent can meet different application scenarios.

[0107] Exemplarily, the mass ratio of the second lithium supplement agent to the first lithium supplement agent can be 10:100, 15:100, 20:100, 25:100, 30:100, 35:100, 40:100, 45:100, 50:100, 55:100, 60:100, 70:100 or a range composed of any two of them.

[0108] In some embodiments, the particle sizes of the first lithium supplement agent and the second lithium supplement agent are in the range of sub-micron to micron scale. The average particle size of the first lithium supplement agent can be greater than that of the second lithium supplement agent, and the order of magnitude of the particle size of the first lithium supplement agent can also be comparable to that of the second lithium supplement agent. When the particle sizes of both the first lithium supplement agent and the second lithium supplement agent are in the micron level, the two materials form secondary particles with a twin structure. When the particle size of the first lithium supplement agent is greater than that of the second lithium supplement agent, the second lithium supplement agent is coated on the surface of the first lithium supplement agent and is wrapped by a carbon coating layer. In both cases, the secondary particles are composed of the first lithium supplement agent and the second lithium supplement agent, and the second lithium supplement agent can play the roles of both a lithium supplement agent and a stabilizer.

[0109] The reduction of the particle size of the second lithium supplement agent shortens the path of lithium ion extraction, increases the interfacial area of delithiation of the second lithium supplement agent, and can obtain more decomposition current during the decomposition delithiation process, thereby reducing the polarization of the first lithium supplement agent during the first charge decomposition process and inhibiting the phase change and the increase of metal valence state of the first material.

[0110] In some examples, the Dv50 of the first lithium supplement agent can be 1μm - 15μm, that is, the particle size corresponding to the cumulative volume percentage reaching 50% in the first lithium supplement agent is 1μm - 15μm. This particle size range is helpful for the processing process of the material particles and the processing stability of the slurry during the pulping process.

[0111] Exemplarily, the Dv50 of the first lithium supplement agent can be 1μm, 2μm, 4μm, 5μm, 7μm, 8μm, 10μm, 11μm, 12μm, 14μm, 15μm or a range composed of any two of them.

[0112] For example, the Dv50 of the first lithium supplement agent can be 1μm - 12μm, and further can be 2μm - 10μm.

[0113] In some examples, the Dv50 of the second lithium supplement agent can be 0.2 μm to 12 μm, that is, the particle size corresponding to the cumulative volume percentage reaching 50% in the second lithium supplement agent is 0.2 μm to 12 μm. This particle size range is helpful for the processing process of the material particles and the processing stability of the slurry during the pulping process.

[0114] Exemplarily, the Dv50 of the second lithium supplement agent can also be 0.2 μm, 0.4 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm or the range composed of any two of them.

[0115] For example, the Dv50 of the second lithium supplement agent can be 0.2 μm to 10 μm, and further can be 0.4 μm to 8 μm.

[0116] In some embodiments, the charge specific capacity of the first lithium supplement agent can be 400 mAh / g to 1200 mAh / g. The first lithium supplement agent is the main lithium supplement agent with a relatively large charge specific capacity, so as to be able to provide more lithium ions and improve the capacity and performance of the battery.

[0117] Exemplarily, the charge specific capacity of the first lithium supplement agent can be 400 mAh / g, 500 mAh / g, 600 mAh / g, 700 mAh / g, 800 mAh / g, 900 mAh / g, 1000 mAh / g, 1100 mAh / g, 1200 mAh / g or the range composed of any two of them.

[0118] The charge specific capacity of the second lithium supplement agent can be 240 mAh / g to 550 mAh / g. The second lithium supplement agent is the auxiliary lithium supplement agent with a relatively small charge specific capacity, so as to be able to assist the first lithium supplement agent to provide lithium ions.

[0119] Exemplarily, the charge specific capacity of the second lithium supplement agent can be 240 mAh / g, 300 mAh / g, 350 mAh / g, 400 mAh / g, 450 mAh / g, 500 mAh / g, 550 mAh / g or the range composed of any two of them.

[0120] In some embodiments, the specific surface area of the cathode lithium supplement agent can be 1 m 2 / g - 20 m 2 / g, so that the cathode lithium supplement agent has higher reaction activity or adsorption capacity.

[0121] Exemplarily, the specific surface area of the cathode lithium supplement agent can be 1 m 2 / g, 2 m 2 / g, 5 m 2 / g, 8 m 2 / g, 10 m2 / g, 12 m 2 / g, 15 m 2 / g, 18 m 2 / g, 20 m 2 / g or a range composed of any two of them.

[0122] For example, the specific surface area of the cathode lithium supplement can be 2 m 2 / g - 18 m 2 / g, and further, it can be 6 m 2 / g - 15 m 2 / g.

[0123] The embodiment of the present application also provides a preparation method of the above-mentioned cathode lithium supplement, including the following steps:

[0124] Mix the first lithium supplement and the second lithium supplement and then perform a sintering treatment to obtain the cathode lithium supplement.

[0125] The above method obtains the cathode lithium supplement through solid-phase mixing and sintering. It does not need to add a solvent, and only needs to mix and sinter the first lithium supplement and the second lithium supplement under solid-phase conditions. The high-temperature solid-phase mixing and sintering method is more efficient and convenient, and is more suitable for industrial production.

[0126] Exemplarily, the first lithium supplement is lithium-rich iron ferrate, and the second lithium supplement is lithium-rich nickelate. During the process of sintering lithium-rich iron ferrate and lithium-rich nickelate into secondary particles, nickel elements in lithium-rich nickelate are doped in lithium-rich nickelate, which improves the structural stability of lithium-rich iron ferrate, increases its conductivity, reduces the polarization effect during the decomposition process. In addition, it not only reduces the risk of iron dissolution in the residues after decomposition but also improves the water absorption failure of lithium-rich iron ferrate particles.

[0127] In some embodiments, the first lithium supplement precursor is subjected to a first sintering treatment to obtain the first lithium supplement, and the second lithium supplement precursor is subjected to a second sintering treatment to obtain the second lithium supplement. After obtaining the first lithium supplement and the second lithium supplement, the first lithium supplement and the second lithium supplement can be mixed and ball-milled so that the second lithium supplement can coat at least part of the surface of the first lithium supplement, or the first lithium supplement can coat at least part of the surface of the second lithium supplement.

[0128] In some embodiments, after mixing and ball-milling the first lithium supplement and the second lithium supplement, a third sintering treatment can be performed with a carbon source, so that carbon coats the surfaces of the first lithium supplement and the second lithium supplement through the third sintering treatment.

[0129] As a specific implementation manner, the first lithium supplement and the second lithium supplement can be crushed to the corresponding particle sizes. For example, the particle size of the first lithium supplement is larger than that of the second lithium supplement. Then, the first lithium supplement and the second lithium supplement are subjected to a sintering treatment.

[0130] In some embodiments, the temperature of the first sintering treatment can be 350°C - 650°C. By setting this temperature range, it helps to obtain a stable lithium supplement agent.

[0131] Exemplarily, the temperature of the first sintering treatment can be 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C or a range composed of any two of them.

[0132] In some embodiments, the temperature of the second sintering treatment can be 350°C - 650°C. By setting this temperature range, it helps to obtain a stable lithium supplement agent.

[0133] Exemplarily, the temperature of the second sintering treatment can be 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C or a range composed of any two of them.

[0134] In some embodiments, the temperature of the third sintering treatment can be 650°C - 900°C. By setting this temperature range, a carbon coating layer can be coated on the surfaces of the first lithium supplement agent and the second lithium supplement agent.

[0135] Exemplarily, the temperature of the third sintering treatment can be 650°C, 700°C, 750°C, 800°C, 850°C, 900°C or a range composed of any two of them.

[0136] As a specific implementation manner, both the first sintering treatment and the second sintering treatment are carried out in a protective atmosphere, and the protective atmosphere includes a nitrogen atmosphere or an argon atmosphere.

[0137] In some embodiments, the time of the first sintering treatment can be 2h - 24h, which helps the second lithium supplement agent to coat on the surface of the first lithium supplement agent.

[0138] Exemplarily, the time of the first sintering treatment can be 2h, 3h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, 22h, 24h or a range composed of any two of them.

[0139] In some examples, the time of the second sintering treatment can be 2h - 24h, which helps the carbon coating layer to coat on the surfaces of the first lithium supplement agent and the second lithium supplement agent.

[0140] Exemplarily, the time of the second sintering treatment can be 2h, 3h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, 22h, 24h or a range composed of any two of them.

[0141] In some examples, the time of the third sintering treatment can be 2h - 24h, which helps the carbon coating layer to coat on the surfaces of the first lithium supplement agent and the second lithium supplement agent.

[0142] Exemplarily, the time of the third sintering treatment can be 2h, 3h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, 22h, 24h or the range composed of any two of them.

[0143] The embodiment of the present application also provides a positive electrode sheet, which includes the above-mentioned positive electrode lithium supplement agent or the positive electrode lithium supplement agent prepared by the above-mentioned preparation method.

[0144] Since the positive electrode sheet of the present application includes the above-mentioned positive electrode lithium supplement agent, it can exhibit excellent lithium supplement effect when applied to a battery.

[0145] In a specific embodiment of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one side of the positive electrode current collector, and the positive electrode active material layer includes the above-mentioned positive electrode lithium supplement agent or the positive electrode lithium supplement agent prepared by the above-mentioned preparation method.

[0146] The positive electrode current collector of the present application can be selected from the positive electrode current collectors commonly used in the art, such as aluminum foil.

[0147] In addition to the positive electrode lithium supplement agent, the positive electrode active material layer of the present application further includes components such as a positive electrode active substance, a conductive agent, and a binder.

[0148] Among them, the positive electrode active substance includes but is not limited to one or more of lithium cobaltate, lithium nickelate, lithium manganate, lithium manganese oxide, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, lithium iron phosphate, lithium nickel manganate, lithium-rich manganese-based material, etc.

[0149] The conductive agent includes but is not limited to one or more of conductive carbon black, Super-C, acetylene black, Ketjen black, carbon nanofibers.

[0150] The binder includes but is not limited to one or more of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC-Na), polyvinylpyrrolidone, polytetrafluoroethylene, styrene-butadiene rubber (SBR).

[0151] In a specific implementation manner, the positive electrode sheet can be prepared by the following method: dispersing the positive electrode active substance, the positive electrode lithium supplement agent, the conductive agent, and the binder in a solvent in proportion to obtain a slurry, and then coating the slurry on at least one surface of the positive electrode current collector, drying, slitting, and rolling to obtain the positive electrode sheet.

[0152] The embodiment of the present application also provides a battery, which includes the above-mentioned positive electrode sheet. Since the battery includes the positive electrode sheet with the positive electrode lithium supplement agent described above, the battery has a higher first-cycle Coulombic efficiency and more excellent cycle performance during use.

[0153] In addition to the above positive electrode sheet, the battery of the present invention further includes a separator and a negative electrode sheet.

[0154] The function of the separator is to separate the positive electrode sheet and the negative electrode sheet, prevent the two from contacting and short - circuiting, and allow lithium ions to pass through freely. It should be noted that during the application process of the separator, the surface of the side with the lithium - supplementing layer is arranged opposite to the separator, so that the lithium - supplementing layer can play the role of supplementing lithium to the positive electrode.

[0155] The separator can be a porous separator commonly used in the art with good chemical stability and mechanical stability, including but not limited to one or more of polypropylene, polyethylene, glass fiber, and non - woven fabric.

[0156] In a possible implementation manner, the separator of the present invention can be obtained by coating or depositing a positive - electrode lithium - supplementing agent on the surface of the separator matrix to form a lithium - supplementing layer, thereby obtaining a separator composite with a lithium - supplementing layer. Among them, coating can be carried out by spraying, spin - coating, slurry coating, etc., and deposition can be carried out by physical deposition or chemical deposition methods.

[0157] Considering the difference in the binding force between the positive - electrode lithium - supplementing agent and different types of separator matrices, a binder can be selected to be added to the lithium - supplementing layer to enhance the bonding strength between the lithium - supplementing layer and the separator matrix, so as to enhance its service performance.

[0158] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. Among them, the negative electrode current collector can be selected from the negative electrode current collectors commonly used in the art, such as copper foil. The composition of the negative electrode active material layer can also refer to the conventional composition in the art. For example, the negative electrode active material layer includes a negative electrode active substance, a conductive agent, and a binder. The negative electrode active substance can be selected from the negative electrode active substances commonly used in the art, including but not limited to one or more of natural graphite, artificial graphite, silicon - carbon materials, silicon - oxygen materials, and hard carbon. The compositions of the conductive agent and the binder can refer to the types of the conductive agent and the binder in the positive electrode sheet, which will not be elaborated here.

[0159] The electrolyte is a medium existing between the positive electrode sheet and the negative electrode sheet for conducting lithium ions. It can be a gel - state, solid - state or liquid - state electrolyte. The present application does not specifically limit the type of the electrolyte, and it can be selected from the gel - state, solid - state or liquid - state electrolytes commonly used in the art.

[0160] In a specific implementation manner, the battery of the present application can be prepared by the following method:

[0161] Disperse the positive electrode active substance, the positive - electrode lithium - supplementing agent, the conductive agent, and the binder in a solvent in proportion to obtain a slurry, and then coat the slurry on at least one side of the positive electrode current collector, and after drying, cutting, and rolling, the positive electrode sheet can be obtained;

[0162] The positive electrode lithium supplement is coated or deposited on the surface of the separator substrate to obtain a separator composite with a lithium supplement layer;

[0163] The negative electrode active material, conductive agent, and binder are dispersed in a solvent in proportion to obtain a slurry, and then the slurry is coated on at least one side of the negative electrode current collector, dried, slit, and roll-pressed to obtain a negative electrode sheet;

[0164] After the positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, a battery cell is obtained through a stacking or winding process, and then through processes such as baking, liquid injection, formation, and encapsulation, the battery of the present application can be obtained.

[0165] The battery of the present application can include the forms of battery cells, battery modules, and battery packs. In some embodiments, the battery cells can be assembled into a battery module. The number of battery cells included in the battery module can be one or more, and those skilled in the art can select the specific number according to the application and capacity of the battery module. In some embodiments, the battery module can also be assembled into a battery pack. The number of battery modules included in the battery pack can be one or more, and those skilled in the art can select the specific number according to the application and capacity of the battery pack.

[0166] There is no particular limitation on the specific type of the battery of the present application. For example, from the perspective of shape, the battery includes but is not limited to square shell batteries, soft pack batteries, cylindrical batteries, etc., and the present application does not make any special restrictions. From the perspective of the electrode core structure, the electrode core of the battery can be a wound electrode core (i.e., a positive electrode sheet, a negative electrode sheet, and a separator are stacked and then made into an electrode core through a winding process), or a stacked electrode core (i.e., multiple positive electrode sheets, negative electrode sheets, and separators are stacked to form an electrode core). The outer shell can be a hard shell (such as a steel shell, a hard plastic shell, etc.) or a soft shell (such as an aluminum plastic film, a bag-type soft shell, etc.). The present application does not make any special restrictions.

[0167] The embodiment of the present application also provides an electrical device including the above battery. The electrical device has the advantages corresponding to the above positive electrode sheet, which will not be elaborated here.

[0168] The electrical device of the embodiment of the present application can be a conventional electrical device in the art, such as a power device (such as an electric vehicle, an electric car), an electronic device (such as a mobile phone, a tablet computer, a laptop computer, a digital camera, etc.), a wearable device (such as a watch, a bracelet, a VR glasses, etc.), an energy storage power station, etc., and no special restrictions are made thereto.

[0169] The battery provided by the present invention, its preparation method, and application will be specifically introduced through specific embodiments below.

[0170] Unless otherwise specified, the reagents, materials, and instruments used in the following examples are all conventional reagents, conventional materials, and conventional instruments in the art, which can be obtained through commercial purchase, and the reagents involved can also be obtained by conventional methods in the art.

[0171] Example 1

[0172] (1) Weigh lithium oxide (Li 2 O) and iron oxide (Fe 2 O 3 ) with a molar ratio of 5.5:1, and mix them to obtain the first lithium supplement precursor.

[0173] (2) Weigh lithium oxide (Li 2 O) and nickel oxide (NiO) with a molar ratio of 1.1:1, and mix them to obtain the second lithium supplement precursor.

[0174] (3) Carry out the first sintering treatment on the first lithium supplement precursor obtained in step (1) at 650 °C for 12 h to obtain the first lithium supplement Li 5 FeO 4 ;

[0175] (4) Carry out the first sintering treatment on the second lithium supplement precursor obtained in step (2) at 650 °C for 12 h to obtain the second lithium supplement Li 2 NiO 2 ;

[0176] (5) Weigh Li 5 FeO 4 and Li 2 NiO 2 obtained from the first sintering treatment, mix them in a 1:1 molar ratio, and ball mill for 2 h;

[0177] (6) Weigh and mix the Li 5 FeO 4 and Li 2 NiO 2 mixture obtained by ball milling with glucose in a ratio of 100:5.

[0178] (7) Carry out the second sintering treatment on the mixture in step (6) at 850 °C for 8 h to obtain a cathode lithium supplement with a carbon coating on the surface;

[0179] (8) Among the cathode lithium supplements obtained in step (7), use a specific surface area of 3 m 2A cathode lithium supplement agent with a Dv50 of 7 μm for the first lithium supplement agent, a Dv50 of 5 μm for the second lithium supplement agent, a mass percentage of the second lithium supplement agent to the first lithium supplement agent of 50%, and a mass percentage of carbon of 2% is mixed evenly with lithium iron phosphate, SP, PVDF, and NMP in a mass ratio of 2:100:2:2.5:60 to form a cathode slurry. The obtained cathode slurry is evenly coated on aluminum foil and dried in vacuum to obtain a cathode sheet.

[0180] (9) Hard carbon, SP, CMC, and SBR are mixed evenly with deionized water in a mass ratio of 90:4:3:3:50, and then coated on an aluminum foil current collector. After drying, it is roll-pressed to obtain a negative electrode sheet.

[0181] (10) The cathode lithium supplement agent is evenly coated on a 14-micron polypropylene (PP) separator and dried in vacuum to obtain a separator.

[0182] (10) The cathode sheet, negative electrode sheet, and separator are stacked in order to obtain a core.

[0183] (11) After the core is cased, an electrolyte of 1 mol / l LiPF 6 (lithium hexafluorophosphate) is injected, and the battery is obtained through formation and grading.

[0184] Example 2

[0185] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 1 m 2 / g, a Dv50 of 7 μm for the first lithium supplement agent, a Dv50 of 5 μm for the second lithium supplement agent, a mass percentage of the second lithium supplement agent to the first lithium supplement agent of 50%, and a mass percentage of carbon of 2% is used.

[0186] Example 3

[0187] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 10 m 2 / g, a Dv50 of 7 μm for the first lithium supplement agent, a Dv50 of 5 μm for the second lithium supplement agent, a mass percentage of the second lithium supplement agent to the first lithium supplement agent of 50%, and a mass percentage of carbon of 2% is used.

[0188] Example 4

[0189] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 20 m 2 / g, a Dv50 of 7 μm for the first lithium supplement agent, a Dv50 of 5 μm for the second lithium supplement agent, a mass percentage of the second lithium supplement agent to the first lithium supplement agent of 50%, and a mass percentage of carbon of 2% is used.

[0190] Example 5

[0191] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 0.2 m 2 / g, Dv50 of the first lithium supplement agent being 7 μm, Dv50 of the second lithium supplement agent being 5 μm, mass percentage of the second lithium supplement agent to the first lithium supplement agent being 50%, and mass percentage of carbon being 2% is used.

[0192] Example 6

[0193] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 21 m 2 / g, Dv50 of the first lithium supplement agent being 7 μm, Dv50 of the second lithium supplement agent being 5 μm, mass percentage of the second lithium supplement agent to the first lithium supplement agent being 50%, and mass percentage of carbon being 2% is used.

[0194] Example 7

[0195] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement agent being 1 μm, Dv50 of the second lithium supplement agent being 5 μm, mass percentage of the second lithium supplement agent to the first lithium supplement agent being 50%, and mass percentage of carbon being 2% is used.

[0196] Example 8

[0197] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement agent being 8 μm, Dv50 of the second lithium supplement agent being 5 μm, mass percentage of the second lithium supplement agent to the first lithium supplement agent being 50%, and mass percentage of carbon being 2% is used.

[0198] Example 9

[0199] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement agent being 15 μm, Dv50 of the second lithium supplement agent being 5 μm, mass percentage of the second lithium supplement agent to the first lithium supplement agent being 50%, and mass percentage of carbon being 2% is used.

[0200] Example 10

[0201] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement agent being 0.2 μm, Dv50 of the second lithium supplement agent being 5 μm, mass percentage of the second lithium supplement agent to the first lithium supplement agent being 50%, and mass percentage of carbon being 2% is used.

[0202] Example 11

[0203] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement agent being 16 μm, Dv50 of the second lithium supplement agent being 5 μm, the mass percentage of the second lithium supplement agent to the first lithium supplement agent being 50%, and the mass percentage of carbon being 2% is used.

[0204] Example 12

[0205] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement agent being 7 μm, Dv50 of the second lithium supplement agent being 0.2 μm, the mass percentage of the second lithium supplement agent to the first lithium supplement agent being 50%, and the mass percentage of carbon being 2% is used.

[0206] Example 13

[0207] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement agent being 7 μm, Dv50 of the second lithium supplement agent being 6 μm, the mass percentage of the second lithium supplement agent to the first lithium supplement agent being 50%, and the mass percentage of carbon being 2% is used.

[0208] Example 14

[0209] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement agent being 7 μm, Dv50 of the second lithium supplement agent being 12 μm, the mass percentage of the second lithium supplement agent to the first lithium supplement agent being 50%, and the mass percentage of carbon being 2% is used.

[0210] Example 15

[0211] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement agent being 7 μm, Dv50 of the second lithium supplement agent being 0.1 μm, the mass percentage of the second lithium supplement agent to the first lithium supplement agent being 50%, and the mass percentage of carbon being 2% is used.

[0212] Example 16

[0213] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement agent being 7 μm, Dv50 of the second lithium supplement agent being 13 μm, the mass percentage of the second lithium supplement agent to the first lithium supplement agent being 50%, and the mass percentage of carbon being 2% is used.

[0214] Example 17

[0215] The difference from Example 1 is that in step (8), a cathode lithium supplement with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement of 7 μm, Dv50 of the second lithium supplement of 5 μm, mass percentage of the second lithium supplement to the first lithium supplement of 10%, and mass percentage of carbon of 2% is used.

[0216] Example 18

[0217] The difference from Example 1 is that in step (8), a cathode lithium supplement with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement of 7 μm, Dv50 of the second lithium supplement of 5 μm, mass percentage of the second lithium supplement to the first lithium supplement of 40%, and mass percentage of carbon of 2% is used.

[0218] Example 19

[0219] The difference from Example 1 is that in step (8), a cathode lithium supplement with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement of 7 μm, Dv50 of the second lithium supplement of 5 μm, mass percentage of the second lithium supplement to the first lithium supplement of 70%, and mass percentage of carbon of 2% is used.

[0220] Example 20

[0221] The difference from Example 1 is that in step (8), a cathode lithium supplement with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement of 7 μm, Dv50 of the second lithium supplement of 5 μm, mass percentage of the second lithium supplement to the first lithium supplement of 8%, and mass percentage of carbon of 2% is used.

[0222] Example 21

[0223] The difference from Example 1 is that in step (8), a cathode lithium supplement with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement of 7 μm, Dv50 of the second lithium supplement of 5 μm, mass percentage of the second lithium supplement to the first lithium supplement of 72%, and mass percentage of carbon of 2% is used.

[0224] Example 22

[0225] The difference from Example 1 is that in step (8), a cathode lithium supplement with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement of 7 μm, Dv50 of the second lithium supplement of 5 μm, mass percentage of the second lithium supplement to the first lithium supplement of 50%, and mass percentage of carbon of 0.1% is used.

[0226] Example 23

[0227] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement agent of 7 μm, Dv50 of the second lithium supplement agent of 5 μm, mass percentage of the second lithium supplement agent to the first lithium supplement agent of 50%, and mass percentage of carbon of 3% is used.

[0228] Example 24

[0229] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement agent of 7 μm, Dv50 of the second lithium supplement agent of 5 μm, mass percentage of the second lithium supplement agent to the first lithium supplement agent of 50%, and mass percentage of carbon of 3% is used.

[0230] Example 25

[0231] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement agent of 7 μm, Dv50 of the second lithium supplement agent of 5 μm, mass percentage of the second lithium supplement agent to the first lithium supplement agent of 50%, and mass percentage of carbon of 0 is used.

[0232] Example 26

[0233] The difference from Example 1 is that in step (8), a cathode lithium supplement agent with a specific surface area of 3 m 2 / g, Dv50 of the first lithium supplement agent of 7 μm, Dv50 of the second lithium supplement agent of 5 μm, mass percentage of the second lithium supplement agent to the first lithium supplement agent of 50%, and mass percentage of carbon of 6% is used.

[0234] Example 27

[0235] The difference from Example 1 is that in step (1), lithium oxide (Li 2 O) and cobalt oxide (Co 3 O 4 ) with a molar ratio of 5.5:1 are weighed and mixed to obtain a first lithium supplement agent precursor.

[0236] Example 28

[0237] The difference from Example 1 is that in step (2), lithium oxide (Li 2 O) and copper oxide (CuO) with a molar ratio of 1.1:1 are weighed and mixed to obtain a second lithium supplement agent precursor.

[0238] Comparative Example 1

[0239] The difference from Example 1 is that steps (2), (4) and (5) are removed, and in step (6), the Li obtained in step (1) 5 FeO 4 and glucose are weighed and mixed in a ratio of 100:5.

[0240] Comparative Example 2

[0241] The difference from Example 1 is that steps (1), (3) and (5) are removed, and in step (6), the Li obtained in step (2) 2 NiO 2 and glucose are weighed and mixed in a ratio of 100:5.

[0242] Performance tests were carried out on the positive electrode lithium supplement, positive electrode sheet, and battery of each example and comparative example respectively, and the performance test results are shown in Table 1.

[0243] 1. Specific surface area

[0244] The positive electrode lithium supplement was tested according to "Determination of Specific Surface Area of Solid Materials by Gas Adsorption BET Method" (GB / T 19587-2017) to measure its specific surface area.

[0245] 2. Particle size Dv50

[0246] The volume particle size distribution of the positive electrode lithium supplement was tested using a Malvern 3000 laser particle size analyzer. For example, GB / T 19077.1 can be referred to.

[0247] 3. Mass ratio of carbon

[0248] The mass ratio of the carbon coating layer to the positive electrode lithium supplement was obtained by thermogravimetric analysis (TGA).

[0249] Principle: Under programmed temperature control, the mass of the substance is measured as a function of temperature or time. The carbon coating layer will burn and decompose at a certain temperature. By recording the mass change of the sample during heating with a thermogravimetric analyzer, the mass ratio of the carbon coating layer can be calculated.

[0250] Operation: Put an appropriate amount of the lithium supplement material sample into the crucible of the thermogravimetric analyzer and heat it to a high temperature at a certain heating rate to completely burn the carbon. According to the mass difference of the sample before and after combustion, the carbon content is calculated.

[0251] 4. Volume ratio after de-lithiation to before de-lithiation

[0252] The volume of the lithium supplement agent before and after delithiation was tested by FIB-SEM. Appropriate sizes (such as 200μm * 200μm) were selected in different regions of the formed electrode sheet, sliced layer by layer and scanned to form multi-layer two-dimensional imaging, and the multi-layer two-dimensional imaging data was reconstructed three-dimensionally. The particle volume occupied by the lithium supplement agent in the electrode sheet will not collapse due to the delithiation of the lithium supplement agent. The sum of the reconstructed volumes occupied by all lithium supplement agents in the selected area is the volume of the lithium supplement agent in this area before delithiation. The volume of the lithium supplement particles after delithiation was also statistically calculated by the above method. The volume ratio before and after delithiation = volume after delithiation / volume before delithiation * 100%.

[0253] 5. Gas generation performance

[0254] The SOC of the battery was adjusted to 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, 0% in sequence. After storing at 60°C for 28 days, the weight of the battery was tested by the water displacement method, and the gas generation amount of the battery was calculated and statistically analyzed through the weight difference.

[0255] 6. Cycling performance: The battery was charged at a constant current (CC) of 0.5C at 45°C until the voltage reached 3.7V, and then switched to constant voltage (CV) charging until the current dropped to 0.05C, at which point the charging process ended. Then, it was discharged at a current of 0.5C until the voltage dropped to 2.3V, and the capacity of the battery at this time was recorded as C1. After cycling 1000 times, the capacity of the battery at this time was recorded as C1000. Check the retention rate of the battery capacity relative to the battery capacity before cycling. The retention rate of the battery capacity = C1000 / C1 * 100%.

[0256] 7. Rate performance: The battery was charged at a constant current (CC) of 0.5C at 25°C until the voltage reached 3.7V, and then switched to constant voltage (CV) charging until the current dropped to 0.05C, at which point the charging process ended. It was discharged at a current of 0.1C until the voltage reached 2.3V, and the capacity of the battery at this time was recorded as C1; it was discharged at a current of 2C until the voltage reached 2.3V, and the capacity of the battery at this time was recorded as C2. The calculation formula for the 2C / 0.1C capacity retention rate is: C2 / C1 * 100%.

[0257] Table 1

[0258] Table 2

[0259]

[0260] The following conclusions can be analyzed from Table 1 and Table 2:

[0261] 1) It can be seen from Examples 1 to 28 and Comparative Examples 1 and 2 that when the specific surface area of the cathode lithium supplement agent, the Dv50 of the first lithium supplement agent, the Dv50 of the second lithium supplement agent, the mass percentage of the second lithium supplement agent to the first lithium supplement agent, and the mass percentage of carbon are within the ranges of the examples of the present invention, it helps to reduce the gas generation amount after lithium deintercalation of the first lithium supplement agent and improve the capacity retention rate of the battery.

[0262] 2) It can be seen from Examples 1 to 6 that when the specific surface area of the cathode lithium supplement agent is in the range of 1 m 2 / g - 20 m 2 / g, it will reduce the gas generation amount after lithium deintercalation of the first lithium supplement agent and improve the capacity retention rate of the battery.

[0263] 3) It can be seen from Examples 1, 7 to 11 that when the Dv50 of the first lithium supplement agent is in the range of 1 μm - 15 μm, it will reduce the gas generation amount after lithium deintercalation of the first lithium supplement agent and improve the capacity retention rate of the battery.

[0264] 4) It can be seen from Examples 1, 12 to 16 that when the Dv50 of the second lithium supplement agent is in the range of 0.2 μm - 12 μm, it will reduce the gas generation amount after lithium deintercalation of the first lithium supplement agent and improve the capacity retention rate of the battery.

[0265] 5) It can be seen from Examples 1, 17 to 21 that when the mass percentage of the second lithium supplement agent to the first lithium supplement agent is in the range of 10:100 - 70:100, it will reduce the gas generation amount after lithium deintercalation of the first lithium supplement agent and improve the capacity retention rate of the battery.

[0266] 6) It can be seen from Examples 1, 22 to 26 that when a carbon coating layer is coated on the surface of the cathode lithium supplement agent and the mass percentage of carbon to the cathode lithium supplement agent is in the range of 0.1% - 5%, it can reduce the gas generation amount after lithium deintercalation of the first lithium supplement agent and improve the capacity retention rate of the battery.

[0267] 7) It can be seen from Examples 27 and 28 and Comparative Examples 1 and 2 that when the specific surface area of the cathode lithium supplement agent, the Dv50 of the first lithium supplement agent, the Dv50 of the second lithium supplement agent, the mass percentage of the second lithium supplement agent to the first lithium supplement agent, and the mass percentage of carbon are within the ranges of the examples of the present invention, when the first lithium supplement agent is Li 6 CoO 4 or the second lithium supplement agent is Li 2 CuO 2 , it can also reduce the gas generation amount after lithium deintercalation of the first lithium supplement agent and improve the capacity retention rate of the battery.

[0268] Finally, it should be noted that: After considering the specification and practicing the invention disclosed herein, those skilled in the art will readily conceive of other embodiments of the present invention. The present invention is intended to cover any variations, uses, or adaptations of the present invention, which follow the general principles of the present invention and include well-known common general knowledge or conventional technical means in the technical field not disclosed in the present invention. It is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A positive electrode lithium supplement, characterized in that: include: a first lithium supplement and a second lithium supplement, wherein one of the first lithium supplement and the second lithium supplement is coated on at least a portion of the surface of the other; The lithium content of the first lithium supplement is higher than the lithium content of the second lithium supplement; The chemical formula of the first lithium supplement includes Li a M b O c , M is at least one of Ni, Cr, Co, Mn, Fe, Al, Cu, V, Ti, and Re; 0<a≤6, 0<b≤3, 0<c≤6; And / or, the chemical formula of the second lithium supplement includes Li x N y O z , N is at least one of Ni, Cr, Co, Mn, Fe, Al, Cu, V, Ti, Ru, and Mo; 0<x≤3, 0<y≤3, 0<z≤4.

2. The positive electrode lithium supplement according to claim 1, characterized in that: The first lithium supplement includes at least one of Li5FeO4, Li6CoO4, Li4CoO4, and Li5ReO6; And / or, the second lithium supplement includes Li2NiO2, Li2RuO3, Li2MnO3, Li2MoO3, Li 0.65 Ni 1.35 At least one of O2.

3. The positive electrode lithium supplement according to claim 1, characterized in that: At least part of the surface of the positive electrode lithium supplement agent is coated with a carbon coating layer.

4. The positive electrode lithium supplement according to claim 3, characterized in that: The mass ratio of the carbon coating layer to the positive electrode lithium supplement agent is 0.1%-5%.

5. The positive electrode lithium supplement according to claim 1, characterized in that: Before the first lithium supplement agent is delithiated, the valence state of M is at least one of +2, +3, +4 and +7; And / or, after the first lithium supplement agent is delithiated, the valence state of M is at least one of +3 and +4.

6. The positive electrode lithium supplement according to any one of claims 1 to 5, characterized in that: The volume of the first lithium supplement after delithiation is 40%-80% of the volume of the first lithium supplement before delithiation; And / or, the volume of the second lithium supplement after delithiation is 70%-90% of the volume of the second lithium supplement before delithiation.

7. The positive electrode lithium supplement according to any one of claims 1 to 5, characterized in that: The delithiation voltage of the first lithium supplement is 3.4V-4.4V; And / or, the delithiation voltage of the second lithium supplement agent is 3.4V-4.5V.

8. The positive electrode lithium supplement according to any one of claims 1 to 5, characterized in that: The mass ratio of the second lithium supplement agent to the first lithium supplement agent is 10:100-70:

100.

9. The positive electrode lithium supplement according to any one of claims 1 to 5, characterized in that: The Dv50 of the first lithium supplement is 1 μm to 15 μm; And / or, the Dv50 of the second lithium supplement is 0.2 μm~12 μm.

10. The positive electrode lithium supplement according to any one of claims 1 to 5, characterized in that: The charging specific capacity of the first lithium supplement agent is 400mAh / g~1200mAh / g; And / or, the second lithium supplement has a specific charge capacity of 240 mAh / g to 550 mAh / g.

11. The positive electrode lithium supplement according to any one of claims 1 to 5, characterized in that: The specific surface area of ​​the positive electrode lithium supplement is 1m 2 / g-20m 2 / g.

12. A method for preparing a positive electrode lithium supplement as claimed in any one of claims 1 to 11, characterized in that: The method comprises: The first lithium replenisher and the second lithium replenisher are mixed and then sintered to obtain the positive electrode lithium replenisher.

13. The preparation method according to claim 12, characterized in that: The first lithium supplement agent and the second lithium supplement agent are mixed and then sintered, comprising: Performing a first sintering treatment on the first lithium supplement agent precursor to obtain the first lithium supplement agent; Performing a second sintering treatment on the second lithium supplement agent precursor to obtain a second lithium supplement agent; The first lithium supplement agent, the second lithium supplement agent and a carbon source are mixed and subjected to a third sintering treatment.

14. The preparation method according to claim 13, characterized in that: The temperature of the first sintering process is lower than the temperature of the third sintering process; And / or, the temperature of the second sintering process is lower than the temperature of the third sintering process.

15. The preparation method according to claim 13 or 14, characterized in that: The temperature of the first sintering treatment is 350°C-650°C; And / or, the temperature of the second sintering treatment is 350°C-650°C; And / or, the temperature of the third sintering treatment is 650° C.-900° C.; And / or, the first sintering treatment time is 2h-24h; And / or, the second sintering treatment time is 2h-24h; And / or, the third sintering treatment time is 2h-24h.

16. A positive electrode sheet, characterized in that: The positive electrode sheet includes the positive electrode lithium replenisher described in any one of claims 1 to 11 or the positive electrode lithium replenisher prepared by the preparation method of the positive electrode lithium replenisher described in any one of claims 12 to 15.

17. A battery, characterized in that: Including the positive electrode sheet as described in claim 16.

18. An electrical equipment, characterized in that: Comprising the battery of claim 17.

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